Harper was branded a hypocrite after he told businesses that improving accessibility was “a no-brainer”, while in September he launched the government’s own Accessible Britain Challenge, challenging “local communities, organisations, councils, and businesses to make their local communities more accessible and more inclusive for disabled people”.

Swinson, whose ministerial responsibilities include the implementation and monitoring of the Equality Act’s public sector equality duty, made similar comments to Harper’s in 2012.

She told her party’s annual conference in September 2012 that “making it harder for people to play an active role in our economy because they are women, or have a disability, or are parents, is a shocking waste of talent”.

She urged the country to “seize the game-changing opportunity that the Paralympics have given us to improve the employment opportunities of people with disabilities”.

And in 2009, backing a petition calling for better access, she said it was “shocking that in the twenty-first century Britain, young disabled [people]are denied access to many services and leisure activities which other young people enjoy”.

Gavin Hamilton, a campaign organiser for Swinson, admitted that her constituency office was “upstairs” in a building in Bearsden, Glasgow, and that a volunteer or member of staff would not be able to work there if they were a wheelchair-user. He also admitted that there was no hearing loop in the office.

Hamilton said – as Harper’s team had done previously – that meetings and constituency surgeries were held elsewhere in the constituency.

But he said: “I understand the issue. If somebody wanted to work here, it is not necessarily wheelchair-friendly.”

“I will of course continue to make any reasonable adjustments necessary for constituents or staff members who have a disability.

“Past examples include paying for a sign language interpreter, undertaking home visits and changing work patterns to accommodate disability.”

But Sally Witcher, chief executive officer of the disabled people’s organisation Inclusion Scotland and a former deputy director of the UK government’s Office for Disability Issues, said the access situation in Swinson’s office was “clearly not acceptable”, particularly because of her role in “exercising leadership around equalities”.

Witcher, also a past chair of the government’s disability employment advisory committee, said: “What a fantastic opportunity to do something positive and what a shame – more than a shame – if that is not the case.

“I would want to know from her what her explanation was for how she thinks this is satisfactory.

“Were I in her shoes, I would find my position very difficult to justify. I don’t know how she thinks it is acceptable.

“Where it is blatantly obvious that there are access issues and they are not removed by those in a position to remove them, that is clearly not acceptable.”

Witcher said she would be “more than happy” to meet the minister to “talk through what action might be taken”.

Inclusion Scotland has been running a pilot scheme, funded by the Scottish government, in which seven disabled graduates have been placed as interns with MSPs.

Witcher said: “It is really about giving disabled people the opportunity to increase their employability but also to have access to the political environment in a way that otherwise might not be available for them.

“The real point is that we have got to start thinking about what access to the political environment really means.”

She said this was not just about disabled constituents, but “about disabled people as interns, employees, civil servants and elected members themselves”.